Abstract
Hydrodynamic experiments on a liquid film are carried out using water in both straight and helical tubes at angles of inclination ranging between 2.5° and 5° and on three different coil diameters (23.86 cm, 32.74 cm and 41.13 cm) for film Reynolds numbers ranging from 100 to 2000. The film thickness is measured by two micrometers, arranged to measure vertical and horizontal distances within the cross section of the tube. The results of film thickness are related to the hydraulic radius to characterize the film flow in both types of tube. Momentum transfer rates are shown to be higher in helical tubes than in the straight incline tube. An empirical correlation is presented for film thickness in the helical tube in terms of NT (coil tube)/NT (straight tube) for film Dean number ranging from 1 to 1000.
Highlights
The occurrence and applications of film flow in chemical engineering processes are numerous; among them are absorption, extraction, heat transfer, humidification and distillation
Hydrodynamic experiments on a liquid film are carried out using water in both straight and helical tubes at angles of inclination ranging between 2.5 ̊ and 5 ̊ and on three different coil diameters (23.86 cm, 32.74 cm and 41.13 cm) for film Reynolds numbers ranging from 100 to 2000
This is a function of hydraulic radius defined by the film boundary
Summary
The occurrence and applications of film flow in chemical engineering processes are numerous; among them are absorption, extraction, heat transfer, humidification and distillation. Hopf (cited in [2]) conducted experiments in a rectangular channel of slope ranging from 0.5 ̊ to 3.5 ̊ and noted the influence of turbulence between the critical film Reynolds numbers (Re , crit) ranging from 250 to 300 He found that wall roughness has no effect on Re ,crit except for the smallest depths. The latest work is concerned with the pipe flow belonging to Yamamoto and co-workers [7,8,9] They studied the laminar and turbulent flow through helical coils. Gupta et al [15] studied the effect of coil pitch and coil diameter on the friction factor for five types of fully filled coils with different radii variation developed for Newtonian fluid They formulated an empirical Equation (9) based on their experimental data. Where a & b are constants and NGe is the Germano number that is equal to Re multiplied by coil curvature
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